Sediment Management

Contaminated Sediment Optimized Remedy

Sediment Management

Background

A Record of Decision (ROD) produced by the EPA for the Lower Fox River Operable Unit 1 (OU1) required a dredging-only method for PCB-contaminated sediments; however, thin sediment deposits with PCB concentrations less than 2.0 ppm covered vast areas of OU1, and created inefficient areas for dredging. GW Partners, LLC, authorized Foth to develop alternative strategies for this “dredge only” ROD that would achieve cleanup objectives, but at a significantly reduced cost. Foth responded to our client’s needs by developing an integrated, optimized remedy.

Approach

Foth’s optimized remedy included evaluating and developing engineered caps, sand covers and dredging as a suite of integrated remedial measures. We first supplemented pre-design data gaps (previously performed by another party for the dredge-only remedy) to enable design of our solution. Foth built a scientifically sound case to help convince the regulatory agencies that alternative remedies were viable, and pursued a ROD Amendment with the EPA to implement a new remedy.

Results

The project was completed nearly five years ahead of the “dredge-only” remedy’s timeline, and at a cost savings of more than $40 million. Long-term monitoring by Foth indicates that our optimized remedy, using a suite of integrated remedial measures, is performing as designed; water quality and fish tissue are responding favorably.

Foth’s targeted characterization sampling used Foth Vibracore™, which saved the client time and money, and greatly reduced the original remedial action’s horizontal footprint. It also yields a high percent of core recovery, which proved critical to accurately map the sediment contamination. The ROD Amendment was secured because of Foth’s 3-D sediment bed modeling, coupled with GIS data management—which when combined, strategically identified customized cost-effective remedies for each sub-area of OU1. Some costs savings were also achieved by using thin layer sand cover and engineered cap designs, in addition to innovative placement methods.

Project Location:
Lower Fox River Operable Unit 1 (OU1), Wisconsin

Awards:

Bentley System's Be Inspired Award - 2013

Foth’s sediment optimized remedy was completed five years ahead of the “dredge-only” timeline, at a cost savings of more than $40 million and with remedial measures continuing to perform as designed.